1. Field of the Invention
The present invention relates to a portable telephone (for example, cellular phone) system and particularly, to a portable telephone system containing a portable telephone terminal which can search the position thereof or the position of another terminal.
2. Description of the Related Art
There has been known a portable telephone terminal (for example, cellular phone) which can search the position thereof or the position of another terminal by using a global positioning system (GPS) satellite or the like. In order to search the position of another terminal, it is necessary to get a password from the other terminal side prior to the searching.
In order to create the password, a combination of, for example, four digits is selected by the user of the other terminal, and the password thus created is transmitted (told) to only persons who are allowed to perform the position search. The transfer of the password may be performed orally or in other manners. A person which the password is transmitted inputs his/her own terminal.
According to the conventional technique described above, the creation and transmission of a password are performed by the user of a portable telephone terminal, and it is strongly required to transmit the password with no leakage, so that advancement of convenience for users has been required to portable telephone terminals.
Passwords are required to be periodically renewed to prevent the leakage thereof, however, the same disadvantage as described above occurs when the passwords thus renewed are transmitted. Further, a password is usually determined by a user so that it corresponds to a sequence of numbers familiar to the user. Therefore, if a past selected password is determined as a renewal password, the countermeasure to the leakage would become insignificant, and thus an improvement in this point has been required.
JPA-11-178047 discloses a wireless portable terminal which can easily get position information of the wireless portable terminal owned by a user. The wireless portable terminal is equipped with incoming-call automatic-answering control means for automatically answering to the incoming call through wireless communications, position information getting means for getting prescribed position information, position information transmitting means for transmitting position information, and control means for controlling the position information getting means to get the position information at the time of the incoming-call automatic answering and controlling the position information transmitting means to transmit the position information to a calling source.
Further, JPA-9-284833 discloses a position search system for mobile terminals in which the position of a mobile terminal to be searched can be determined with no telephone call. The position search system comprises search-side mobile terminals for searching the latest current positions of mobile terminals to be searched, and mobile terminals to be searched which are located in wireless areas (cells) which are not necessarily coincident with the wireless areas of the search-side mobile terminals. Each mobile terminal to be searched includes storage means for inputting and storing the latest current position information thereof, and transmission means for transmitting the latest current position information when predetermined personal identification number and search code transmitted from a search-side mobile terminal are received and coincident with those of the mobile terminal concerned to be searched.
However, the JPA-11-178047 discloses no technique of getting the position information of another portable telephone terminal, and the JPA-9-284833 has no disclosure of a specific method of creating passwords (personal identification numbers). Therefore, it is difficult to improve the convenience by using even these techniques.